Power transmission apparatus of hybrid electric vehicle

ABSTRACT

A power transmission apparatus of a hybrid vehicle including an engine and a first motor-generator and a second motor-generator includes a compound planetary gear set engaged to a first motor shaft of the first motor-generator, and configured to receive an engine torque from the engine through a one-way clutch, to receive a motor torque of the first motor-generator, and to output an output torque as a combination of the engine torque and the motor torque through a drive gear, a motor shaft gear fixedly connected to a second motor shaft of the second motor-generator, and an output shaft disposed in parallel to and between an engine torque shaft connected to the engine and the second motor shaft connected to the second motor, and gear-meshed with the drive gear and the motor shaft gear respectively through a driven gear.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2021-0188084 filed on Dec. 27, 2021, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE PRESENT DISCLOSURE Field of the Present Disclosure

The present disclosure relates to a power transmission apparatus of ahybrid vehicle.

Description of Related Art

An environment-friendly technology of a vehicle is a core technologywhich controls survival of a future vehicle industry, and advancedvehicle makers have focused their energy on the development of anenvironment-friendly vehicle to achieve environmental and fuelefficiency regulations.

Therefore, vehicle makers have developed an electric vehicle (EV), ahybrid electric vehicle (HEV), a fuel cell electric vehicle (FCEV), andthe like, as future vehicle technologies.

Because the future vehicle has various technological restrictions suchas a weight and cost, the vehicle makers have paid attention to thehybrid electric vehicle as an alternative of a realistic problem formeeting exhaust gas regulations and improving fuel efficiencyperformance and have entered into keen competition for commercializingthe hybrid electric vehicle.

The hybrid electric vehicle is a vehicle using two or more powersources. Two or more power sources may be combined by various schemesand a gasoline engine or a diesel engine using the existing fossil fueland a motor-generator driven by electrical energy are mixed and used asthe power sources.

In the hybrid electric vehicle, an EV mode in which the hybrid electricvehicle is driven by only the motor, an HEV mode using both the engineand the motor, and an ENG mode using only the engine may be implementedaccording to the combination of the engine and the motor.

Furthermore, the hybrid electric vehicle can provide a significantimprovement of fuel efficiency through an idle stop function of stoppingthe engine when the vehicle stops, and also through a regenerativebraking, where a motor-generator is driven as a generator to generateelectricity by a kinetic energy of the vehicle under a brakingsituation, such generated electricity is stored in a battery, and thestored electricity is reused in driving the vehicle.

The information included in this Background of the present disclosuresection is only for enhancement of understanding of the generalbackground of the present disclosure and may not be taken as anacknowledgement or any form of suggestion that this information formsthe prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present disclosure are directed to providing apower transmission apparatus of a hybrid vehicle including an engine anda first motor-generator and a second motor-generator, including acompound planetary gear set engaged to a first motor shaft of the firstmotor-generator, and configured to receive an engine torque from theengine through a one-way clutch, to receive a motor torque of the firstmotor-generator, and to output an output torque as a combination of theengine torque and the motor torque through a drive gear, a motor shaftgear fixedly connected to a second motor shaft of the secondmotor-generator, and an output shaft disposed in parallel to and betweenan engine torque shaft connected to the engine and the second motorshaft connected to the second motor, and gear-meshed with the drive gearand the motor shaft gear respectively through a driven gear.

The compound planetary gear set may include a common planet carrierconfigured to rotatably support both of a first planetary gear and asecond planetary gear having different diameters, the common planetcarrier including a planet carrier shaft connected to the engine torqueshaft through the one-way clutch, a first sun gear gear-meshed with thefirst planetary gear and fixedly connected to the first motor shaft, andconfigured to selectively act as a fixed element, a second sun geargear-engaged to the second planetary gear, and configured to selectivelyact as a fixed element, and a ring gear gear-meshed the first planetarygear, and fixedly connected to the drive gear.

The first planetary gear and the second planetary gear may be integrallyformed to have a same rotation speed, and the first planetary gear mayhave a diameter greater than the second planetary gear.

The first sun gear may be selectively connectable to a transmissionhousing through a first brake. The second sun gear may be selectivelyconnectable to the transmission housing through a second brake.

The output shaft may be gear-meshed with a final reduction gear of adifferential through an output gear.

A power transmission apparatus of a hybrid vehicle according to anexemplary embodiment enables shifting of the engine speed to anincreased speed for a high speed or medium speed driving, improving fuelefficiency.

Furthermore, a one-way clutch is disposed between the engine torqueshaft and the planet carrier shaft of the compound planetary gear set,and thereby, in two EV modes, torques of the first motor-generator andthe second motor-generator may not affect the engine without employing aseparate clutch.

Furthermore, in the compound planetary gear set, torques of the engineand the first motor-generator are combined by first and second planetarygears and having different diameters sharing a common planet carrier andfirst and second sun gears externally gear-meshed with the planetarygears, and thereby two EV modes and two HEV PARALLEL modes, increasingshift ratio span.

Furthermore, electricity may be generated by supplying some of thetorque of the engine to the first motor-generator in the HEV E-CVT mode,and thereby energy regeneration efficiency may be enhanced.

Furthermore, in two HEV PARALLEL modes, a sufficient driving torque maybe achieved by the torque assistance of the second motor-generator, forexample, on a sloped road.

Other effects which may be obtained or are predicted by an exemplaryembodiment will be explicitly or implicitly described in a detaileddescription of the present disclosure. That is, various effects that arepredicted according to an exemplary embodiment will be described in thefollowing detailed description.

The methods and apparatuses of the present disclosure have otherfeatures and advantages which will be apparent from or are set forth inmore detail in the accompanying drawings, which are incorporated herein,and the following Detailed Description, which together serve to explaincertain principles of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a power transmission apparatus of ahybrid vehicle according to an exemplary embodiment of the presentdisclosure.

FIG. 2 is an operation chart of a power transmission apparatus of ahybrid vehicle according to an exemplary embodiment of the presentdisclosure.

FIG. 3 , FIG. 4 , FIG. 5 , FIG. 6 , and FIG. 7 illustrate power flow inshifting modes of a power transmission apparatus of a hybrid vehicleaccording to an exemplary embodiment of the present disclosure,respectively.

It may be understood that the appended drawings are not necessarily toscale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the present disclosure.The specific design features of the present disclosure as includedherein, including, for example, specific dimensions, orientations,locations, and shapes will be determined in part by the particularlyintended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present disclosure throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent disclosure(s), examples of which are illustrated in theaccompanying drawings and described below. While the presentdisclosure(s) will be described in conjunction with exemplaryembodiments of the present disclosure, it will be understood that thepresent description is not intended to limit the present disclosure(s)to those exemplary embodiments of the present disclosure. On the otherhand, the present disclosure(s) is/are intended to cover not only theexemplary embodiments of the present disclosure, but also variousalternatives, modifications, equivalents and other embodiments, whichmay be included within the spirit and scope of the present disclosure asdefined by the appended claims.

Exemplary embodiments of the present disclosure will be described morefully hereinafter with reference to the accompanying drawings, in whichexemplary embodiments of the present disclosure are shown. As thoseskilled in the art would realize, the described embodiments may bemodified in various different ways, all without departing from thespirit or scope of the present disclosure.

To clarify the present disclosure, portions that are not related to thedescription will be omitted, and the same elements or equivalents arereferred to with the same reference numerals throughout thespecification.

In the following description, dividing names of components into first,second, and the like is to divide the names because the names of thecomponents are the same as each other, and an order thereof is notparticularly limited.

FIG. 1 is a schematic diagram of a power transmission apparatus of ahybrid vehicle according to an exemplary embodiment of the presentdisclosure.

Referring to FIG. 1 , a power transmission apparatus of a hybrid vehicleaccording to an exemplary embodiment of the present disclosure iscoupled to power sources of an engine ENG and first and secondmotor-generators MG1 and MG2.

A power transmission apparatus of a hybrid vehicle includes a compoundplanetary gear set PU configured to combine the torque of the engine ENGand the torque of the first motor-generator MG1, a motor shaft gearMSG2, and an output shaft OS configured to receive torques from theplanetary gear set PU and the second motor-generator MG2 and to outputan output torque to a differential DIFF.

The engine ENG is a power source, and may be implemented as one ofvarious types such as a gasoline engine or a diesel engine.

The first and second motor-generators MG1 and MG2 are also powersources, and may function as a motor as a generator, respectively. Eachof the first and second motor-generators MG1 and MG2 includes a statorfixed to a transmission housing H and a rotor rotatably supported at aradially internal side of the stator.

The engine ENG outputs an engine torque through an engine torque shaftEOS, and the engine torque shaft EOS is disposed on a same axis with afirst motor shaft MS1 of the first motor-generator MG1.

The compound planetary gear set PU is disposed on the first motor shaftMS1 of the first motor-generator MG1.

In the compound planetary gear set PU, first and second planetary gearsP1 and P2 are carried by a common planet carrier PC, and a planetcarrier shaft PCS formed at a rotation center portion of the planetcarrier PC is connected to the engine torque shaft EOS through a one-wayclutch OWC.

Here, the first planetary gear and the second planetary gear P1 and P2are formed with different diameters but integrally formed to rotate at asame rotation speed. At the instant time, the first planetary gear P1may have a diameter greater than the second planetary gear P2.

Furthermore, the one-way clutch OWC is configured to transfer only thetorque of the engine ENG to the compound planetary gear set PU, and notto transfer the torque of the compound planetary gear set PU to theengine ENG.

In the compound planetary gear set PU, a first sun gear 51 is externallygear-meshed with the first planetary gear P1, and a second sun gear S2is externally gear-meshed with the second planetary gear P2.

Here, each of the first and second sun gears 51 and S2 may beselectively connectable to the transmission housing, to selectively actas a fixed element.

That is, the first sun gear 51 may be selectively connectable to thetransmission housing H through a first brake B 1, and the second sungear S2 may be selectively connectable to the transmission housing Hthrough a second brake B2.

Here, the first brake and the second brake B1 and B2 may be realized asmulti-plate hydraulic pressure friction devices that are frictionallyengaged by hydraulic pressure.

Furthermore, the first sun gear S1 is fixedly connected to the firstmotor shaft MS1.

The compound planetary gear set PU includes a single ring gear R, wherethe ring gear R is internally gear-meshed with the first planetary gearP1, and fixedly connected to a drive gear DG.

It may be understood that the planetary gear set PU receives torquesthrough the sun gear S and the planet carrier PC and is configured tovary the received torque (by increasing or decreasing the speed) and tooutput the varied torque through the ring gear R.

Furthermore, the motor shaft gear MSG2 is fixedly connected to a secondmotor shaft MS2 of the second motor-generator MG2. Here, the secondmotor shaft MS2 is disposed in parallel with the first motor shaft MS1.

The output shaft OS is disposed in parallel to and between the enginetorque shaft EOS and the second motor shaft MS2, and provided with adriven gear PG fixedly connected thereto, where the driven gear PG isexternally gear-meshed with the drive gear DG and the motor shaft gearMSG2, respectively.

Furthermore, the output shaft OS is also provided with an output gear OGwhich is fixed thereto and externally gear-meshed with a final reductiongear FDG of the differential DIFF.

That is, the output shaft OS receives torques from the compoundplanetary gear set PU and the second motor-generator MG2 through thedriven gear PG, and outputs the received torque to the differential DIFFthrough the output gear OG.

Gear ratios between the drive gear DG, the driven gear PG, and the motorshaft gear MSG2 may be appropriately set according to desired feature ofthe transmission.

FIG. 2 is an operation chart of a power transmission apparatus of ahybrid vehicle according to an exemplary embodiment of the presentdisclosure. FIG. 3 , FIG. 3 , FIG. 4 , FIG. 5 , FIG. 6 , and FIG. 7illustrate power flow in shifting modes of a power transmissionapparatus of a hybrid vehicle according to an exemplary embodiment ofthe present disclosure, respectively.

Referring to FIG. 2 and FIG. 3 , FIG. 3 , FIG. 4 , FIG. 5 , FIG. 6 , andFIG. 7 , according to operations of the engine ENG and the first andsecond motor-generators MG1 and MG2 and an operation of the first brakeand the second brake B1 and B2, five operation modes may be achieved asfollows.

[EV1 Mode]

Referring to FIG. 2 and FIG. 3 , in the EV1 mode, while none of thefirst brake and the second brake B1 and B2 is operated, the operation ofthe engine ENG is stopped, and the second motor-generator MG2 is drivenforward.

Accordingly, the second motor-generator MG2 is operated by electricalenergy of a battery, and the torque of the second motor-generator MG2 istransferred to the differential DIFF through the second motor shaft MS2,the motor shaft gear MSG2, the driven gear PG, the output shaft OS, theoutput gear OG, and the final reduction gear FDG, realizing the EV1mode.

For example, the EV1 mode may be achieved in a low speed driving below30 km/h.

Furthermore, driving rearward may be enabled when the secondmotor-generator MG2 is driven backward in the above condition.

[EV2 Mode]

Referring to FIG. 2 and FIG. 4 , in the EV2 mode, while only the secondbrake B2 is operated, the operation of the engine ENG is stopped, thefirst motor-generator MG1 is driven backward, and the secondmotor-generator MG2 is driven forward.

Accordingly, in the compound planetary gear set PU, the second sun gearS2 acts as a fixed element. Accordingly, the torque of the firstmotor-generator MG1 is input to the first sun gear S1 of the compoundplanetary gear set PU through the first motor shaft MS1 and increased inspeed, and the increased speed is output through the drive gear DGconnected to the ring gear R.

Furthermore, the torque of the first motor-generator MG1 output to thedrive gear DG is combined with torque of the second motor-generator MG2at the driven gear PG, and transferred to the differential DIFF throughthe output shaft OS, the output gear OG, and the final reduction gearFDG, realizing the EV2 mode.

For example, such EV2 mode may be realized in a high load situation suchas a sloped road.

Furthermore, driving rearward may be enabled when the firstmotor-generator MG1 is driven forward and the second motor-generator MG2is driven backward in the above condition.

[HEV E-CVT Mode]

Referring to FIG. 2 and FIG. 5 , in REV E-CVT mode, in a neutral statewhere none of the first brake and the second brake B1 and B2 isoperated, the one-way clutch OWC functions, the engine ENG is operated,and the second motor-generator MG2 is driven forward.

Accordingly, the torque of the engine ENG is input to the planet carrierPC of the compound planetary gear set PU through the engine torque shaftEOS. Accordingly, some of engine torque is provided to the first motorshaft MS1 of the first motor-generator MG1 through the first sun gear S,and the other of the engine torque is output to the drive gear DGconnected to the ring gear R.

Accordingly, the first motor-generator MG1 may be driven to generateelectricity to recharge the battery by the partial torque of the engineENG.

Furthermore, the torque of the engine ENG output to the drive gear DG iscombined with torque of the second motor-generator MG2 at the drivengear PG, and transferred to the differential DIFF through the outputshaft OS, the output gear OG, and the final reduction gear FDG,realizing the HEV E-CVT mode.

[HEV PARALLEL 1 Mode]

Referring to FIG. 2 and FIG. 6 , in the HEV PARALLEL 1 mode, the one-wayclutch OWC and the first brake B1 are operated, the engine ENG isoperated, and the second motor-generator MG2 is driven forward.

Accordingly, in the compound planetary gear set PU, the first sun gearS1 acts as a fixed element. Accordingly, the torque of the engine ENG isinput to the planet carrier PC of the compound planetary gear set PUthrough the engine torque shaft EOS and increased in speed, and theincreased speed is output through the drive gear DG connected to thering gear R.

Furthermore, the torque of the engine ENG output to the drive gear DG iscombined with the torque of the second motor-generator MG2 at the drivengear PG when the second motor-generator MG2 is operated, and transferredto the differential DIFF through the output shaft OS, the output gearOG, and the final reduction gear FDG, realizing the HEV PARALLEL 1 mode.

At the present time, the operation of the second motor-generator MG2 maybe an operation for torque assistance of the engine ENG.

[HEV PARALLEL 2 Mode]

Referring to FIG. 2 and FIG. 7 , in the HEV PARALLEL 2 mode, the one-wayclutch OWC and the second brake B2 are operated, the engine ENG isoperated, and the second motor-generator MG2 is driven forward.

Accordingly, in the compound planetary gear set PU, the second sun gearS2 acts as a fixed element. Accordingly, the torque of the engine ENG isinput to the planet carrier PC of the compound planetary gear set PUthrough the engine torque shaft EOS and increased in speed to a higherrotation speed compared to the HEV PARALLEL 1 mode, and the increasedspeed is output through the drive gear DG connected to the ring gear R.

Furthermore, the torque of the engine ENG output to the drive gear DG iscombined with the torque of the second motor-generator MG2 at the drivengear PG when the second motor-generator MG2 is operated, and transferredto the differential DIFF through the output shaft OS, the output gearOG, and the final reduction gear FDG, realizing the HEV PARALLEL 2 mode.

At the present time, the operation of the second motor-generator MG2 maybe an operation for torque assistance of the engine ENG.

As described above, a power transmission apparatus of a hybrid vehicleaccording to an exemplary embodiment enables shifting of the enginespeed to an increased speed for a high speed or medium speed driving,improving fuel efficiency.

Furthermore, a one-way clutch is disposed between the engine torqueshaft EOS and the planet carrier shaft PCS of the compound planetarygear set PU, and accordingly, in two EV modes, torques of the first andsecond motor-generators MG1 and MG2 may not affect the engine ENGwithout employing a separate clutch.

Furthermore, in the compound planetary gear set PU, torques of theengine ENG and the first motor-generator MG1 are combined by first andsecond planetary gears P1 and P2 having different diameters sharing acommon planet carrier PC and first and second sun gears S1 and S2externally gear-meshed with the planetary gears P1 and P2, and therebytwo EV modes and two HEV PARALLEL modes, increasing shift ratio span.

Furthermore, electricity may be generated by supplying some of thetorque of the engine ENG to the first motor-generator MG1 in the HEVE-CVT mode, and thereby energy regeneration efficiency may be enhanced.

Furthermore, in two HEV PARALLEL modes, a sufficient driving torque maybe achieved by the torque assistance of the second motor-generator MG2,for example, on a sloped road.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”,“upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”,“inwardly”, “outwardly”, “interior”, “exterior”, “internal”, “external”,“forwards”, and “backwards” are used to describe features of theexemplary embodiments with reference to the positions of such featuresas displayed in the figures. It will be further understood that the term“connect” or its derivatives refer both to direct and indirectconnection.

Furthermore, the term of “fixedly connected” signifies that fixedlyconnected members always rotate at a same speed. Furthermore, the termof “selectively connectable” signifies “selectively connectable membersrotate separately when the selectively connectable members are notengaged to each other, rotate at a same speed when the selectivelyconnectable members are engaged to each other, and are stationary whenat least one of the selectively connectable members is a stationarymember and remaining selectively connectable members are engaged to thestationary member”.

The foregoing descriptions of specific exemplary embodiments of thepresent disclosure have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent disclosure to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the present disclosure and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present disclosure, as well asvarious alternatives and modifications thereof. It is intended that thescope of the present disclosure be defined by the Claims appended heretoand their equivalents.

What is claimed is:
 1. A power transmission apparatus of a hybridvehicle including an engine and a first motor-generator and a secondmotor-generator, the power transmission apparatus comprising: a compoundplanetary gear set engaged to a first motor shaft of the firstmotor-generator, and configured to receive an engine torque from theengine through a one-way clutch, to receive a motor torque of the firstmotor-generator, and to output an output torque as a combination of theengine torque and the motor torque through a drive gear; a motor shaftgear fixedly connected to a second motor shaft of the secondmotor-generator; and an output shaft disposed in parallel to and betweenan engine torque shaft connected to the engine and the second motorshaft connected to the second motor, and gear-meshed with the drive gearand the motor shaft gear respectively through a driven gear.
 2. Thepower transmission of claim 1, wherein the compound planetary gear setincludes: a first planetary gear and a second planetary gear havingdifferent diameters, a common planet carrier configured to rotatablysupport the first planetary gear and the second planetary gear andincluding a planet carrier shaft coupled to the engine torque shaftthrough the one-way clutch; a first sun gear gear-meshed with the firstplanetary gear and fixedly connected to the first motor shaft, andconfigured to selectively act as a first fixed element; a second sungear gear-engaged to the second planetary gear, and configured toselectively act as a second fixed element; and a ring gear gear-meshedthe first planetary gear, and fixedly connected to the drive gear. 3.The power transmission of claim 2, wherein the first planetary gear andthe second planetary gear are integrally formed to have a same rotationspeed.
 4. The power transmission of claim 2, wherein the first planetarygear has a diameter greater than a diameter of the second planetarygear.
 5. The power transmission of claim 2, further including: a firstbrake and a second brake, wherein the first sun gear is selectivelyconnectable to a transmission housing through the first brake, andwherein the second sun gear is selectively connectable to thetransmission housing through the second brake.
 6. The power transmissionof claim 5, wherein the first brake is mounted to the first motor shaftand the transmission housing.
 7. The power transmission of claim 5,wherein the second brake is mounted to the second sun gear and thetransmission housing.
 8. The power transmission of claim 2, wherein thesecond sun gear is rotatably mounted on the first motor shaft.
 9. Thepower transmission of claim 1, wherein the output shaft fixed to thedriven gear is gear-meshed with a final reduction gear of a differentialthrough an output gear.
 10. The power transmission of claim 5, wherein,in an EV1 mode, while none of the first brake and the second brake isoperated, operation of the engine is stopped, and the secondmotor-generator is driven forward, in an EV2 mode, while only the secondbrake is operated, the operation of the engine is stopped, the firstmotor-generator is driven backward, and the second motor-generator isdriven forward, in an HEV E-CVT mode, in a neutral state where none ofthe first brake and the second brake is operated, the one-way clutchfunctions, the engine is operated, and the second motor-generator isdriven forward, in an HEV PARALLEL 1 mode, the one-way clutch and thefirst brake are operated, the engine is operated, and the secondmotor-generator is driven forward, and in an HEV PARALLEL 2 mode, theone-way clutch and the second brake are operated, the engine isoperated, and the second motor-generator is driven forward.